1. Field of the Invention
The present invention relates to wireless Local Area Network (LAN) system. More particularly, the present invention relates to a method of guaranteeing a user's anonymity and a wireless LAN system therefor, by using a temporary address generated from a unique Media Access Control (MAC) address as a source address or a destination address.
2. Description of the Related Art
Generally, a wireless LAN system consists of an ad-hoc network where a plurality of terminals, each of which includes a wireless Network Interface Card (NIC), are connected to each other and independently to wired LANs, and an infrastructure network where wireless terminals are connected to wired LANs through wireless access nodes. In an infrastructure network, a wireless cell Basic Service Set (BSS) is formed centering on one wireless access node. The wireless access node has the same functionality as a cellular phone station and connects all wireless terminals in the BSS to a LAN.
FIG. 1 illustrates a conceptual scheme showing the structure of a wireless LAN system of a general infrastructure network. A wireless LAN system as shown in FIG. 1 consists of a wireless access node 11 and four wireless terminals 13, 15, 17, and 19. The wireless access node 11 is connected to a wired network, such as very-high-speed Internet lines or private lines, and performs access arbitration between wireless terminals. The four wireless terminals 13, 15, 17, and 19 form a BSS and include wireless LAN cards respectively. The wireless LAN cards installed respectively in the first to fourth wireless terminals 13, 15, 17, and 19 have MAC addresses MAC Addr1 to MAC Addr4 corresponding to the first to fourth wireless terminals 13, 15, 17, and 19.
The unique MAC addresses MAC Addr1 to MAC Addr4 allocated to the respective wireless LAN cards of the first to fourth wireless terminals 13, 15, 17, and 19 are used as source addresses or destination addresses when sending and receiving data packets between the first through fourth wireless terminals 13, 15, 17, and 19 through the wireless access node 11. That is, to transmit a data packet (for example, a protocol data unit (PDU)) to one wireless terminal among the first to fourth wireless terminals 13, 15, 17, and 19, the wireless access node 11 sends transmission frames 12, 14, 16, and 18, each of which contain a unique MAC address (i.e., a MAC address among the first to fourth MAC addresses MAC Addr1 to MAC Addr4) of a wireless terminal representing the destination address. The address is placed in the header of the data packet (PDU) to be transmitted. On the other hand, each of the first to fourth wireless terminals 13, 15, 17, and 19 compares the MAC address corresponding thereto with the destination addresses contained in the headers of the transmission frames 12, 14, 16, and 18 sent from the wireless access node 11. If a destination address is identical to the MAC address corresponding to a wireless terminal, the corresponding wireless terminal accepts the frame. If no match is made, the frame is dropped over the network.
MAC addresses used for data communication between wireless terminals through wireless access nodes are unique values allocated upon manufacturing wireless LAN cards. The MAC address is not varied and also is not encoded. Accordingly, MAC addresses are exposed during data communication so that anonymity of a user using a corresponding MAC address cannot be guaranteed. Thus, a user using the corresponding MAC address may be easily tracked. That is, by merely monitoring unique MAC addresses, private user information about network access states, network access time, etc., may be outflowed, and more seriously, if any unique MAC address is exposed, a greater risk exists for malicious users eavesdropping at the link layer. Further, the possibility of an attack on the encryption channels is increased in long-running monitoring.
As described above, since it is necessary to guarantee a user's anonymity so that information about a user of a wireless LAN system is not leaked to objects other than a permitted entity, the conventional wireless LAN system of the infrastructure network has many security problems.